Multiple Myeloma

Multiple Myeloma

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Monoclonal Gammopathy of Undetermined Significance

Monoclonal gammopathy of undetermined significance (MGUS) is a condition in which an abnormal protein — known as monoclonal protein or M protein — is in your blood. The protein is produced in a type of white blood cell (plasma cells) in your bone marrow.

MGUS usually causes no problems. But sometimes it can progress over years to other disorders, including certain forms of blood cancer like multiple myeloma.

MGUS occurs when abnormal plasma cells produce M protein often in adults over the age of 40. The protein isn't harmful for most people. But if too much M protein accumulates, it crowds out healthy cells in your bone marrow and can damage other tissues in your body.

Types of MGUs

There are three main types of MGUs and based on the size and type of expression a doctor may advise frequency of screening

Type of MGU Description
Non-IgM MGUs This is the most common type of MGUs seen in the body and has the potential to progress to multiple myeloma
IgM MGUs About 15% - 20% of patients express the IgM MGU. It can potentially progress to a rarer form of cancer called as "Waldenstrom macroglobulinemia" and rarely to multiple myeloma
Light chain MGUS (LC-MGUS) These MGUS can progress to a condition in which a certain type of M protein is found in the urine protein (Bence Jones proteinuria) and develop into light chain multiple myeloma

WHO Disease Classification

PLASMA CELL NEOPLASMS or cancers in the plasma cell are classified as the following as per WHO guidelines

Cancer Type Sub-types
Monoclonal gammopathy of undetermined significance (MGUS) No Sub-types
Multiple Myeloma
  • Symptomatic i.e. showing symptoms of myeloma
  • Asymptomatic or Smoldering i.e. the disease does not show any active symptoms
  • Nonsecretory
  • Plasma Cell Leukemia
  • Solitary plasmacytoma of bone
  • Extra medullary plasmacytoma
Deposition Disease
  • Primary Amyloidosis
  • Systemic Heavy and Light Chain Disease
Osteosclerotic Myeloma (POEMS Syndrome) No Sub-types

We have focused on Multiple Myeloma & Plasmacytoma in this article topic today.

Multiple Myeloma Staging

There are 2 common systems of staging the disease. Both are comprehensive

Durie-Salmon Staging

Disease Stage Hemoglobin Level Serum Calcium Bone X ray M-Component Proteins
Stage I 10g/dl Normal levels or 12mg/dl Normal or solitary plasmacytoma
  • IgG value < 5g/dL
  • IgA value < 3g/dL
  • Bence Jones protein < 4g/24 hr)
Stage II Stage III > values > stage I Stage III > values > stage I Stage III > values > stage I Stage III > values > stage I
Stage III 12g/dl
  • Type A: Relatively normal renal function (serum creatinine value < 2.0 mg/dL)
  • Type B: Abnormal renal function (serum creatinine value =2.0 mg/dL)
Advanced Stage lesions
  • IgG value > 7g/dL
  • IgA value >5g/dL
  • Bence Jones protein >12g/24 hr)

International Staging System for Myeloma (2005)

Stage Criteria
Stage I
  • Serum albumin ≥ 3.5 g/dL
  • Serum β2-microglobulin (read as beta2-microglobulin) < 3.5 mg/L
Stage II Neither Stage I or Stage III
Stage III Serum β2-microglobulin > 5.5 mg/L


Type of Plasmacytoma Description
Solitary Plasmacytoma of Bone

    This occurs earlier than multiple myeloma (almost as long as a decade earlier) and is more common in males

    SPEP is ideally negative but in almost 50% of the patients a low level of M protein may be present. Bone Marrow usually does not show increased plasma cells

  • Solitary plasmacytoma is usually diagnosed by
    • Biopsy-proven solitary lesion of bone or soft tissue with evidence of clonal plasma cells
    • Normal bone marrow with no evidence of clonal plasma cells
    • MRI/PET-CT Scans
    • Absence of end-organ damage such as hypercalcaemia, renal insufficiency, anaemia, or bone lesions (CRAB)
Extramedullary Plasmacytoma

    The common sites of involvement are the nasal cavity, nasopharynx, larynx and sinuses. It can happen in any location in the body and is commonly of the IgA sub-type. Other evidence of systemic Multiple Myeloma is typically absent

  • Solitary plasmacytoma is usually diagnosed by
    • No M-Protein in serum and/or urine
    • Normal bone marrow
    • Extramedullary tumor of clonal plasma cells
    • Absence of end-organ damage such as hypercalcaemia, renal insuffi ciency, anaemia, or bone lesions (CRAB)

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